Understanding Structural Destabilization and Amyloid Aggregation in ALS-Related Neurodegenerative Disorder: An In...

Area of Science:

• Biochemistry and Molecular Biology
• Neuroscience
• Structural Biology

Background:

• Protein misfolding and aggregation are hallmarks of neurodegenerative diseases.
• Superoxide dismutase 1 (SOD1) requires metal ions for proper folding and function; metal absence (apo form) can induce misfolding and aggregation.
• Mutations in SOD1 are implicated in amyotrophic lateral sclerosis (ALS).

Purpose of the Study:

• To investigate the impact of mutations and metal deficiencies on SOD1 aggregation.
• To elucidate the role of the metal binding loop in SOD1 misfolding and amyloid formation.
• To understand the structural and thermodynamic changes associated with SOD1 aggregation in ALS pathogenesis.

Main Methods:

• Computational approaches including Molecular Dynamics (MD) simulations.
• Experimental techniques: Dictionary of Secondary Structure in Proteins (DSSP), Fourier-transform infrared (FTIR) spectroscopy, Circular dichroism (CD) spectroscopy, ANS fluorescence, Congo red and Thioflavin T (ThT) fluorescence assays, and Transmission Electron Microscopy (TEM).
• Thermodynamic stability studies using Guanidine hydrochloride (GdnHCl).

Main Results:

• Apo-SOD1 exhibits significant conformational differences and increased beta-sheet formation compared to holo-SOD1, indicating aggregation propensity.
• Mutations and metal deficiencies expose hydrophobic pockets and reduce thermodynamic stability, promoting amyloid and amorphous aggregate formation.
• Experimental and computational data consistently show that apo/holo SOD1 variants induce aggregate formation under physiological conditions.

Conclusions:

• Mutation/metal deficiency, particularly in loop IV, and reduced disulfide bonds synergistically destabilize SOD1, driving aggregation.
• The findings highlight the critical role of metalation status and structural integrity in SOD1's aggregation pathway.
• This research provides a foundation for developing novel therapeutic strategies targeting SOD1 aggregation in neurodegenerative diseases like ALS.